Third round of thorium test irradiation starts

31 January 2018

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The irradiation of two fuel pins containing thorium-plutonium oxide pellets is under way at the Halden research reactor in Norway. Thor Energy - which is leading the consortium carrying out the research - said this is the start of the third phase of a five-year trial-operation of thorium-based nuclear fuels.

The thorium-MOX pellets were produced at the Institute for Energy Technology's (IFE's) nuclear fuel laboratory at Kjeller, near Oslo. The pellets were produced with thorium oxide provided by Solvay. These were loaded into two fuel pins and assembled into a test rig - together with a reference pin containing uranium oxide pellets - that was loaded into the OECD Nuclear Energy Agency's Halden research reactor.

The loading of the test rig into the Halden reactor (Image: IFE)

The Halden reactor allows for continuous data collection while the fuel operates in the reactor, hence the need for fully instrumented test fuel pins and rigs. The data acquired is necessary to confirm that the fuel could be implemented safely and productively in a commercial reactor.

"This is the first time industrial-type thorium-MOX pellets have been fabricated and irradiated with a focus on commercial deployment," Thor Energy said yesterday.

The thorium fuel is in the form of pellets composed of a dense thorium oxide ceramic matrix containing about 10% of finely blended plutonium oxide as a 'fissile driver'. As a mixed-oxide (MOX) fuel variant it is familiar to the nuclear industry, but thorium-MOX fuel has certain advantages compared to the uranium-MOX fuels in use at some reactors around the world. It promises higher operating safety margins due to higher thermal conductivity and melting point, and produces no new plutonium as it operates. Thor Energy says thorium-plutonium fuels therefore provide a new option for reducing civil and military plutonium stocks.

The first thorium fuel specimens were loaded into the Halden reactor, operated by IFE, in April 2013, with the second batch loaded in December 2015. Both rigs were intended to verify test results.

Øystein Asphjell, CEO of Thor Energy, said: "We have spent the last five years developing the fuel recipe and the skills to successfully produce these pellets. Through this loading of fuel in Halden, we have reached a major milestone and an important stepping stone towards commercial approval for thorium-based fuels in existing light water reactors. We believe this represents a further step in the thorium evolution which will contribute to the long-term sustainability of nuclear power in general."

The Thorium Irradiation Consortium was launched in 2011 and led by Thor Energy and has IFE, Westinghouse, Finland's Fortum, the UK's National Nuclear Laboratory, the EU Joint Research Centre at Karlsruhe and the Korea Atomic Energy Research Institute as consortium partners.